A typical high efficiency internal combustion engine (e.g., gasoline, diesel, etc.) has an operating efficiency of approximately 35%. As such, approximately 35% of the chemical energy within the fuel gets converted into the mechanical energy that drives the wheels and auxiliary systems of the vehicle in which the engine is installed. Approximately 60% of the fuel's chemical energy is lost as thermal energy through the engine's devices, such as its exhaust and cooling systems. The prior art discloses various concepts directed to the recovery of thermal energy lost through the devices of an internal combustion engine.
In one example, U.S. Pat. No. 4,366,674 to Eakman is directed to a system that uses a Rankine vapor power cycle to recover thermal energy from the exhaust and cooling system with the aid of a vapor powered turbocharger. An automobile's engine has to operate under varying loads so to overcome the slow response of the engine and system to increased load demands Eakman uses an afterburner, which has the negative effect of increasing fuel consumption and increasing recovery demands on overall system. An automobile's engine is under non-steady state operation, so with varying loads and cycle flow rates, the Rankine cycle has negative effects of poor stability for liquid going to re-circulating pump, high recirculation losses and thermal loss at the condenser making it not practical in an automobile's engine.
In another example, U.S. Pat. No. 6,089,020 to Kawamura is directed to a heat recovering apparatus for use in a cogeneration system with an engine. The apparatus includes several turbochargers in series, one turbocharger is driven by the engine's exhaust gas, and another turbocharger driven by an energy recovering turbine comprising an exhaust gas turbine and a steam turbine driven by steam generated by a ceramic heat exchanger which indirectly heats water from the exhaust gas that is downstream of the turbochargers.
In a further example, U.S. Pat. No. 7,454,911 to Tafas is directed to an energy recovery system and method of using the same. The system is configured so that the exhaust gas from the engine flows through a steam generating boiler then to an exhaust turbine. The steam generated by the boiler then flows to the steam turbine that has a common shaft with the exhaust turbine which then drives an electric generator. The steam that leaves the steam turbine is condensed and pumped through the engine's fluid cooling circuit and back to the boiler. This system can only appropriately be used on engines that power hybrid type automobiles so the electrical energy can be utilized. Also, because of varying loads and rotational speed of an automobile's engine, there will be flow differentials across the two turbine wheels causing one wheel to retard the second based on engine operating conditions. Additionally, condensing the steam and pumping the water through engine block and back into boiler induces flow and fluid stability challenges due to automobile engines needing the ability operate at idle and full load within a few seconds.
What is needed is a system and method that will overcome the flow balance and fluid stability challenges and higher recirculation losses of the prior recovery systems for use on an internal combustion engine. The present invention will fulfill this need as well as other needs.
The exemplification set out herein illustrates one embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.